Embodiments of the invention are directed to apparatus and methods for preparing dielectric films. More specifically, embodiments of the invention are directed to apparatus and methods for the treatment of deposited dielectric films with 3D conformality and good electrical and physical properties.
The scaling of semiconductor devices, such as dynamic random access memory (DRAM), logic devices, and the like, may be limited by gate leakage (Jg). For example, as thickness of a gate dielectric layer is scaled, current may leak between the channel and the gate of a transistor device causing device failure. The gate leakage may be reduced by incorporating nitrogen into the gate dielectric layer. For example, a gate dielectric layer at the 32 nm node may comprise silicon oxynitride (SiON), where the presence of nitrogen reduces gate leakage in the device.
Typically, nitrogen is incorporated into the gate dielectric layer by a plasma nitridation process that provides for gate leakage reduction at the expense of other desired properties, for example, flat band voltage (Vfb), threshold voltage (Vt), and mobility. For example, increased nitrogen content in the gate dielectric layer may undesirably increase Vt and excessively decrease mobility. Further, oxygen may diffuse from the gate dielectric layer under typical processing conditions, thus further reducing device performance, for example by degrading the dielectric properties of the gate dielectric layer.
Besides nitridation of dielectric films, there are other post-treatment processes, for example, densification of deposited films. As the thermal budget imposes more restriction on processing temperature, dielectric deposition is moving towards low temperature processes. However, low temperature processes suffer from poor electrical and physical properties. Dielectric films with 3D conformality and good electrical and physical properties are extremely important for next generation of devices. To realize conformal film (good step coverage) at low temperature, CVD or ALD deposition processes are commonly used. These films generally require plasma treatment or other treatments to improve the film quality. Currently, plasma treatment of semiconductor features suffers from non-conformality. This means that, for example, the side wall(s) of the features (e.g., trenches), are treated to a different extend compared to the top and bottom of the feature.
Accordingly, there is an ongoing need in the art for methods and apparatus to achieve more conformal treatment of deposited or formed films.